The instructions of the field section fall in 4 categories: - setting various parameters - plotting and printing - understanding the field - service instructions The use of this section is fairly straight-forward since there is only one frequently used instruction in this section: PLOT. ------------------------------------------------------------------------ Setting parameters: ------------------------------------------------------------------------ AREA Sets the view and size of the plotting area GRID Sets the density of the plotting grid SELECT Establishes the list of sense wires TRACK Sets the track used for graphs ------------------------------------------------------------------------ Plotting and printing: ------------------------------------------------------------------------ PLOT General purpose field plotting instruction PRINT General purpose field printing instruction ------------------------------------------------------------------------ Understanding: ------------------------------------------------------------------------ CHECK Verifies charges and boundary conditions MULTIPOLE-MOMENTS Computes the multipole moments for a wire ------------------------------------------------------------------------ Service instructions: ------------------------------------------------------------------------ SAMPLE Field value (see also CALL ELECTRIC_FIELD) TIME Times the field calculations Note 1: there are several instructions in the optimisation section that perform related tasks. Note 2: there are also procedure calls that perform related tasks: ELECTRIC_FIELD, ELECTRIC_FIELD_3, INTEGRATE_CHARGE, INTEGRATE_FLUX and MAP_INDEX.
Sets the part of the chamber that is being looked at, and optionally also sets the projection. AREA commands are found in several sections: - field section: where the command establishes the plane on which e.g. contours are plotted - drift sections: where the command limits the region over which particles are allowed to drift and sets the viewing direction for plots of drift lines - optimisation section: shares both the field and the drift area, respectively to set the optimisation plane and to limit drift lines - signal section: shares the drift area The geometrical aspects of the field and the drift area are distinct, but the viewing plane is shared between the two. Format: AREA [xmin ymin xmax ymax | xmin ymin zmin xmax ymax zmax] ... [VIEW plane] ... [ROTATE angle] ... [X-Y | R-PHI | X-Z | Y-Z | 3D | CUT] ... [LIGHT-ORIGIN phi_light theta_light] ... [REFLECTED-FRACTION frac_refl] ... [SCATTERED-FRACTION frac_scat] ... [PARTIAL-BOX-TICKMARKS | FULL-BOX-TICKMARKS] ... [PARTIAL-TUBE | FULL-TUBE] ... [PARTIAL-PLANES | FULL-PLANES] ... [SPLIT-INTERSECTING-PLANES | NOSPLIT-INTERSECTING-PLANES] ... [NOSORT-PLANES | SORT-PLANES] ... [OUTLINE | NOOUTLINE] ... [PLOT-MAP | NOPLOT-MAP] ... [NOSTEP | STEP] Example: AREA -1 -1 1 1
Additional Information on:
If the default coordinate axes in the viewing plane (see the topic "plane_coordinates") do not suit you, then you can rotate these axes by an amount you specify with this keyword. The angle should be specified in degrees. [Default rotation angle: 0 degrees.]
Additional Information on:
(Mainly a debugging instruction.) Checks the field calculations. The WIRE option, however, is often used to determine the field at the surface of the wires - since this determines to a large extent the avalanche amplification. Format: CHECK [WIRES] ... [EPSILON-WIRE eps_wire] ... [CHARGES] ... [PLANES] ... [TUBE] ... [MAXWELL] ... [BINS bins] ... [EPSILON-MAXWELL eps_Maxwell] ... [PRINT | NOPRINT] ... [PLOT | NOPLOT] ... [FULL] ... [NOKEEP-RESULTS | KEEP-RESULTS] Example: CH WIRE BINS 50 (This would be used to find the field on the surface of the wires and you'll get a few checks on the wire-charges for free.)
Additional Information on:
Sets the number of grid points in x (or r) and y (or phi) used to produce the plots and tables. [Default is 25 for both.] The second arguments may be omitted in which case the first value will be used for both the x (or r) and the y (or phi) spacing. Format: GRID number_of_steps_in_x [number_of_steps_in_y] Example: GRID 50
Helps in finding wires that have a clear dipole, quadrupole etc moment because of the presence of other wires nearby. Such wires should receive special attention because Garfield assumes that a simple charge is enough to describe the wire. The absence of dipole, quadrupole etc potentials in Garfield is not a fundamental limitation. Such potentials can be added on request. Format: MULTIPOLE-MOMENTS ... WIRE wire ... [ORDER order] ... [RADIUS r] ... [NOPLOT | PLOT] ... [NOPRINT | PRINT] ... [EPSILON eps] ... [ITERATE-MAXIMUM iter] Example: MULTIPOLE WIRE 1 PLOT Will plot the multipole moments up to order 4 for wire 1.
Additional Information on:
Enters global and local options. Only the local options are listed here. Format: OPTIONS [NOCHECK-MAP-INDICES | CHECK-MAP-INDICES] ... [CONTOUR-ALL-MEDIA | CONTOUR-DRIFT-MEDIUM] Example: opt check-map contour-drift
Additional Information on:
This instruction plots the electrostatic and magnetic field in a variety of ways. CPU time can be saved if several plots are combined in a single command. Similar instructions exist in the drift and signal sections. Format: PLOT-FIELD [CONTOUR [f1] [RANGE {cmin cmax | AUTOMATIC}] ... [N n] ... [LABELS | NOLABELS] ] ... [GRAPH [f2]] [ON f_curve] ... [N n]] ... [SCALE min max] ... [NOPRINT | PRINT] ... [HISTOGRAM [f3] [RANGE {hmin hmax | AUTOMATIC}] ... [BINS nbin]] ... [SURFACE [f4] [ANGLES phi theta]] ... [VECTOR [f5 f6 [f7]]] If you don't manage to fit all this on a single line, remember that lines that end on an ellipsis are continued on the next. Examples: PLOT HIST VECTOR SURF CONT PLOT CONTOUR RANGE 500 550 PLOT GRAPH 'SIN X' (The first example makes most of the plots using default functions and ranges - useful as a first call. The second example makes a more detailed contour plot and the third one shows that you can use this program also to produce graphs of arbitrary functions.)
Additional Information on:
Prints a table of a series of field functions (using X, Y or R, PHI and EX, EY or ER, EPHI plus BX, BY, Bz if applicable as symbolic names). A large number of functions may be given as argument but the tables are always for at most 4 functions at the time. This instruction tends to produce a lot of output: (GRID/10)**2 pages. Format: PRINT f1 f2 ... Example: PR EX, EY, E, V
Evaluates and prints the field at a single point. This instruction was used for debugging - but is now superseded by the procedure call ELECTRIC_FIELD and ELECTRIC_FIELD_3. Format: SAMPLE x y Example: SAMPLE 0.5 0.5
Selects and groups the sense-wires. The grouping is of no importance in this section. The selection determines which wires are checked by CHECK. The argument string consists of wire-codes and/or wire-numbers. Format: SELECT wire_selection Example: SEL (1 S) 2 F (Put wire 1 together with all S wires in one group, make wire 2 a group of its own and do the same for each of the F wires.)
Times the field evaluation n [default: 1000] times. Format: TIME [n] Example: TIME 10000
Defines the track used by the PLOT GRAPH instruction. Format: TRACK x_start y_start x_end y_end Example: TR -1 -1 -1 1